科研之友
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摘要
Sandy conglomerate formations were widely deposited in the petroleum bearing basins in China and are critical components of the backup reserves for major oilfields. Hydraulic fracturing is commonly utilized in developing the thick conglomerate formations with porosity smaller than 0.1 and permeability less than 1 md. However, significant challenges are encountered in fracturing. The higher-than-normal surface pressure leaves limited chance for stages with higher proppant concentrations. Some operators suffer from pre-mature screenout during fracturing. Laboratory studies were performed to correlate the pressure drop across the fractures with conglomerate diameter, conglomerate arrangement, fluid viscosity, proppant concentration, proppant size and pump rate. Rock samples used in this study were 1 m long and 0.4 m wide. The range of the parameters was selected based on field design and lab applicability. Based on the experimental data, a handy correlation was developed to predict the pressure loss in sandy conglomerate fractures. This correlation was used to assist the post fracturing pressure matching in fracture modeling. Different from conventional pressure matching where a simple tortuosity calculation equation was used, this application utilized the new correlation that considered the fracturing design, rock and fluid properties. This correlation can also be incorporated into any fracture modeling software so that the net pressure can be more accurately calculated by considering the pressure loss across the rough conglomerate surfaces. Experimental data showed that the significant fracture surface roughness created by the conglomerates dictates the pressure drop across the fractures. An increase in proppant concentration, proppant size, gel viscosity, pump rate and the volumetric fraction of conglomerates in the rock induces higher pressure loss which can be predicted by the newly proposed correlation. By incorporating the new correlation into fracture modeling, the upgraded modeling tool has more reliable pressure history matching. This tool facilitates the fracturing design in sandy conglomerate reservoirs by optimizing proppant concentrations and pump rate in later stages without pre-mature pressure-out.
- 出版日期2015-9
- 单位中国石油大学（华东）
